1. Field of the Invention
This invention relates to railway cars and particularly to an articulated multi-unit railway car capable of optimum efficiency in operation.
2. Description of the Prior Art
Hopper cars have long been used in the railroad industry to transport bulk commodities, such as minerals, grain, certain chemicals and the like. Typically, a hopper car includes a covered or open top, through which the transported material is loaded, and a bottom discharge system. Bulk materials of the type previously described are predominantly transported in one hundred ton hopper cars having cubic capacities suitable for the densities of the commodities to be carried. The empty weights of those cars vary according to their volumetric capacities. The largest of the one hundred ton covered hopper cars in the United States and Canadian railcar fleets used to transport the materials previously described possess a volumetric capacity of 4,550 to 4,750 cubic feet. Open top hopper cars have volumes of 3,600 cubic feet up to 4,200 cubic feet. The empty weight of these large cars is in the range of 60,000 to 65,000 pounds. A hundred ton hopper car of such designs can be loaded to a gross weight of 263,000 pounds. The weight carrying capacity of each car is the difference between the gross weight-on-rail and empty car weight; therefore, cars having an empty weight of 60,000 to 65,000 pounds have respective carrying capacities of 203,000 to 198,000 pounds. A standard hopper car generally is a relatively long vehicle, such as having an overall coupler to coupler length of about 60 feet and a length of 45'-9" between truck centers. Because railroad clearances for right of ways in the Un:;ted States, Mexico, and Canada are defined by Association of American Railroads (AAR) clearance diagrams, the width of a standard hopper car having the foregoing truck center length is restricted to 10'-51/4".
One hundred ton covered hopper cars are equipped with industry approved standard components, including two each 100 ton three piece trucks, two each draft rigging sill assemblies with couplers, and one set of body mounted or truck mounted airbrake systems. The cars are also constructed with straight or curved sides, trough-type or round roof openings for loading, and sloping bottoms leading to three or four outlet gates for unloading. The conventional cars are further equipped with safety devices or appliances such as ladders, handbrakes, uncoupling rods, sill steps, roof running boards or walkways, crossover platforms, all designed and built to meet the requirements of Federal Railroad Administration (FRA) standards. The underframe construction is either a through center sill or shear plate and stub sill design. The underframe of such known hoppers incorporate the use of transverse body bolsters and longitudinal side sills that extend the length of the car for proper distribution of dead and live loads imposed on the structures. These cars are designed and built for interchange service between railroads and conform to standard specifications formulated by the AAR. The foregoing cars have been the industry standard for the transportation of bulk commodities since the early 1960s. Open top hopper cars have a similar design except for the elimination of the roof and associated equipment.
An indicative evaluation of the carrying capacity of a hopper car for bulk commodities is determined by computing the ratios of volume to lightweight, and load limit to lightweight. For a standard covered hopper car having a volume of 4,750 cubic feet and weighing 63,000 pounds, the volume to lightweight ratio is 0.0754 and the load limit to lightweight ratio is 3.175. In addition, these known hopper cars provide an approximate load limit to length ratio (i.e. 200,000 lbs./60 feet) of 3333.0 and a volume/length ratio (4,750 cu. ft./60 feet) of 79.2. The foregoing efficiencies and factors have been the generally expected limit for existing hopper cars. The railroad industry has become aware of the critical need to reduce the initial capital investment cost as well as day to day operating costs of its equipment. The previously described hopper cars, such as of the one hundred ton design, suffer serious drawbacks when considering the relative cost of the equipment and the overall efficiency of operation. There exist numerous areas from a operational standpoint in which improvements in efficiency should be highly desired by the industry. For example, known covered hopper cars possess an inefficient aerodynamic design and excessive weight that results in fuel inefficiency.
The maintenance cost for standard covered cars is also undesirably high. Costly maintenance can be directly attributed to the standard number of components in the design, such as the number of trucks and the like, that are required in a trainset of a large number of cars as is common. Existing hoppers have also demonstrated a relatively poor accident record, increasing costs by virtue of damage to the equipment and subsequent lading losses. All of the foregoing factors have a significant impact on the expected operating expense of standard hopper cars. Manufacturing costs of hopper cars as currently used are further dependent on the size and weight of the equipment for a given trainset. Because of the inherent design of current hopper cars, there is little hope of making any significant impact on the costs of manufacturing and maintenance. Accordingly, a critical need exists in the industry for new designs of hopper cars for carrying commodities that offer real savings in manufacturing and operating costs.